Rs232 have different voltage levels than TTL. Therfore communication with real RS232 devices we need a TTL to RS232 level converter. If you want to send data between two UARTS both working with the same voltage. No level conversion is needed

Don't confuse the voltage levels/signal descriptions with the message format. RS-232 & TTL are voltage levels. What you send over the comm. lines is up to you: 5,6,7,8,9,etc. bits per byte, Odd, even, fixed-level or no parity; 1, 1.5, 2, 3, 4, etc. stop bits/idle. You could even start with more than one start bit.

The common formats allow equipment by different manufacturers to communicate with each other, but if you do not care about that, you can use any format your heart desires.

Proof by example, here is a PC serial port connected to a MAX3235 , all connected to an oscilloscope.

In red channel 1, a probe x10 on the wire 3 of the DB9, so Tx of RS232 .
In blue channel 2, a probe x10 on the leg of a max3235 , so Rx of TTL .

The PC is sending two characters in C 9600-8N1.

So:
* In Idle line is at 1. -10V in RS232 & +5V in TTL
* The start bit S is set to 0
* 8 bits of data for C, the ASCII character 0x43 or b01000011, knowing that the LSB is transmitted first
* The stop bit S' at 1.
* To the next character ...